An Ice Core Reveals How Profoundly The Black Death Changed Medieval Society

In the year of the Lord 1347, the Black Death arrived in Europe. Introduced by merchants coming from Asia, the plague, caused by the bacterium Yersinia pestis, spread quickly. Following trading routes, in just six years this incurable disease killed 25 million people, one-third of the population on the continent. Entire villages were wiped out, some cities lost 80% of their citizens. The plague was followed by famine. Thomas Basinus (1412-1491), bishop of Èvreux and later historian, notes that ‘many peasants fled or died so that many fields remained uncultivated or there was nobody left to care.’ In the cities, overpopulation and poor hygiene helped to spread the plague, rivers were used to dispose of the many corpses, contaminating the water. Riots of desperate people were common, like in 1323 in Flanders and in 1358 in France. Many believed, as one witness testified, that the end of the world had arrived.

The Triumph of Death is a painting by Pieter Bruegel the Elder, painted c. 1562 it was inspired by the waves of the Black Death plaguing the 14th century.

The dramatically reduced population had, however, a surprisingly beneficial effect on the environment. The pollution of the air dropped to a historic low.

Atmospheric circulation transported the lead from the lowlands into the Alps, where it was washed out from the atmosphere by rain and snow. The snow, accumulating mostly during winter, partially melts and changes over the summer into ice, forming single layers, as found in a glacier. By analyzing the concentration of elements in the single layers, it is possible to create an annual record of the atmospheric deposition. One significant spike can be found around 1349-1353 when the measured concentration of lead dropped far below the average value of 10^2 nanogram of lead per liter air. Even today, after the introduction of unleaded fuel in the 1980s, the concentration of lead in the air is still 10 times higher as in 1350.

Reconstructed lead concentration in the last 2,000 years and most important mining districts. Image Source & Credit MORE et al. 2017. CC BY-NC-ND 4.0

In medieval times, lead was used for roofing of large buildings such as cathedrals, water pipes, but especially for dishes and glazed pottery valued by the rich. The most important lead ore is galena. As galena also contains silver, it was widely mined (silver, lead, and copper were the most important metals in medieval Europa). The most productive mines were found on the British island, South Italy, the Harz mountains with Freiberg in Saxony and Kutna Hora in Bohemia. We know of contemporary records of the silver medieval monarchs received as royalties, that the mines of Freiberg and Kutna Hora alone provided 20 tons of silver and 100 tons of lead per year. To get this amount, it was necessary to mine and process an almost 2,000 times larger quantity of rocks and ore. The Black Death impacted mining in two ways. The miners and workers died in great number, and many mines were abandoned. As the population died, including the rich people, the demand for lead also dropped.

The Black Death was so deadly, mining for lead virtually stopped and no lead dust, coming from both mining as smelting, was dispersed into the environment. As the atmosphere became cleaner, the concentration of lead deposited in the glaciers of the Alps dropped.

Entrance to a medieval mine in the Alps, dated around 1530.

The Black Death had a disastrous impact and yet helped to create modern Europe. Plagued previously by overpopulation and poverty, Europe could reinvent itself after the Black Death made the old political system obsolete. Many peasants at the time were virtually slaves, owned by the rich landlords. As the landlords were gone, many people were free to choose where and when to settle. The surviving landlords, in desperate need of somebody to take care of their properties, agreed to lower the taxes and more privileges were granted to farmers. Wages everywhere increased, as healthy workers were rare, and the land became cheaper. Many previously poor people managed to achieve some wealth. Authorities even tried to forbid the use of fur in clothing, a privilege reserved only to the aristocracy in former times, but now common. Political and social independence was now possible and a new class rose from the ashes of the old society — the free citizen. A new human being for a new epoch, as the Renaissance was later seen by historians. However, even after 1353, the Black Death didn’t completely disappear. Almost once in a decade, a smaller outbreak was reported, but improved hygiene in the cities, quarantine procedures, and an acquired genetic immunity of the survivors reduced the risk of infection significantly.

This societal development can also be seen in the studied ice core. Just some years after the plague of 1347-1353, the concentration of lead significantly increased, approaching values seen before the Black Death. The European mining industry experienced a boom in the 15th and 16th century, testified also by many active mines found now also in the Alps. Only recently the concentration of lead started to drop again, in response to efforts to ban this toxic element from daily use and improved environmental regulations. However, it is still an important metal, mostly used for batteries in the automobile industry.